Biomedical subjects
Publications and source records attributed to J H Exon.
Mice exposed to subclinical doses of cadmium chloride for ten weeks and inoculated with antigen six weeks after discontinuance of exposure had a remarkable decrease in antibody-forming cells, particularly IgG. These results indicate that immunosuppression produced by environmental contaminants may persist for several months after exposure to the contaminant.
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Mice fed 1, 5, and 10 ppm methylmercury plus 6 ppm selenium for 10 wk had a significant increase in antibody synthesis. Since methylmercury singly depresses antibody synthesis and the response was greater than that produced by selenium alone, synergism between methylmercury and selenium occurred. In this case, the synergism is considered to be advantageous to a host, while exposure by other combinations of environmental contaminants may be detrimental. Mercury concentrations in the kidney were markedly elevated when methylmercury and selenium were administered simultaneously compared to when methylmercury was given without selenium supplement. These results indicate that data collected from individual pollutants may not be of value in predicting responses to multiple exposure.
Polycythemia developed in progeny from mothers who were exposed during pregnancy to a combination of methylmercury chloride plus ethylurea and sodium nitrite. The polycythemia occurred as early as one month of age and as many as 24% of the offspring developed the polycythemic condition. Many features of this condition are similar to those of polycythemia vera in man, such as elevated hematocrits and white and red blood cell counts, splenomegaly, and hyperplasia of bone marrow accompanied by megakaryocytosis.
Simultaneous exposure to lead and cadmium is highly probable due to common environmental sources of exposure. Mice were exposed simultaneously for 10 wek to lead and cadmium and effects were observed on accumulation of the metals in tissues and susceptibility to viral challenge. The incidence of viral-induced mortality was enhanced in all groups of mice exposed to lead and suppressed in groups of mice treated with cadmium. Mice exposed to both lead and cadmium had mortality rates intermediate to those observed after exposure to the individual metals. Lead and cadmium residues in tissues of mice exposed to both metals, as compared to residues in tissues of mice which received lead or cadmium only, indciated that interaction occurs in regard to metabolism, storage, and excretion of these elements. Chronic coexposure to lead and cadmium appears to alter certain effects produced by exposure to each metal alone.
An experimental protocol was designed to assess humoral immune responses in animals antigenically challenged without the aid of adjuvants. The antigen selected was keyhole limpet hemocyanin (KLH). An enzyme-linked immunosorbent assay (ELISA) was utilized as the technique to measure serum antibody levels. The procedure was tested for sensitivity by use of a known immunosuppressant (cyclophosphamide), two metals (lead and selenium), and three chlorinated hydrocarbons (polychlorinated biphenyls, pentachlorophenol, and toxaphene). KLH without adjuvant provoked an adequate humoral immune response when assessed by the ELISA. The antibody response was greater on d 15 than on d 8 following primary KLH challenge, while secondary challenge resulted in an additional 10-fold increase in antibody levels. Cyclophosphamide suppressed the later primary response (d 15) and the secondary response more so than the early primary response (d 8). Of the 5 chemicals tested, 4 resulted in significantly impaired antibody levels to KLH at some time during the response. The magnitude of the immune response elicited to KLH is compared to that reported for bovine serum albumin and ovalbumin administered with Freund's adjuvant.
Male Swiss Webster mice were exposed to one of three different cadmium salts (sulfate, acetate and chloride) in the drinking water for 10 weeks and then inoculated with a 14-day LD75 or LD35 dilution of encephalomyocarditis virus. the incidence of viral-induced mortality was lower in 17 of the 18 cadmium-treated groups of mice as compared to controls. Cadmium tissue residues and histopathologic lesions were essentially similar at comparable doses in all groups of mice regardless of the form of cadmium in the diet.